First fix the keyword in the boards table. View your Boards and see where the wrong keyword is with this SQL Query.
SELECT * FROM w3t_Boards
Change it to the right keyword with a query like this:
UPDATE w3t_Boards
SET Bo_Keyword = 'newkeyword'
WHERE Bo_Keyword = 'oldkeyword'
Then you need to find what (incorrect) keyword is assigned to a post you've moved. Take note of the post number (in the url of the "moved" link) and use it in this query.
SELECT B_Board FROM w3t_Users WHERE B_Number = xxxxxxx
That'll show the incorrect keyword. Take note of that.
Now reattach the posts to the forum using the newkeyword you defined above in the w3t_Boards table.
UPDATE w3t_Posts SET B_Board = 'newkeyword'
WHERE B_Board = 'wrongkeyword'
Make sense?